The present invention relates generally to an improved filter means to be utilized to remove particulate solids, such as dust particles from particle-laden or dust-laden air flow, and more specifically to a means for imparting shaking motion to a filter for controlled removal of particles from the surface thereof through parametric resonant vibration of the filter barrier material such as the filter bags which form the solids separation media for the filtering means.
In the treatment of dust-laden air, filter envelopes or bags are frequently employed and in operation, these envelopes or bags are normally between an inlet and an outlet of a plenum enclosure which, simply stated, forms the filter chamber. During use, the filters, the surfaces of which form the separation medium in the plenum become laden with solid undesirable particles such as dust, or solid valuable particles, such as may be produced in a manufacturing operation; these particles being periodically removed in order to reduce the pressure drop which builds up across the active surface of the filter medium. Inasmuch as a pressure differential is employed to move the dust or other particle-laden air through the filter chamber, build-up of solids on the filter medium surface will cause an increase in the pressure differential and consequent decrease in air flow. Depending upon the application, various adverse results can occur. For example, dust-cake build up in a floor sweeping machine results in an increase in filter pressure differential and consequent flow rate reduction in the normal dust controlling air flow. Drop in air flow, if unchecked, results in ultimate loss of dust control and the escape of dust around the machine and into the ambience.
As indicated, one common application of dust control apparatus is use in combination with a floor sweeping machine, such as a self-propelled or mobile power sweeping machine. These devices normally employ a vacuum or pressure source to establish a pressure differential for passing dust-laden air through the filter envelopes or bags so as to remove the dust from the air being transferred. Normally, means are provided to shake or vibrate the filter envelopes or bags so as to periodically remove the entrapped solid dust particles, thereby effectively cleaning the filters and reducing the back pressure across the filter elements. Other common applications for filter installations arranged to separate particulate solids from a stream of air include stationary applications such as found in a bag house or small stationary type filter arrangements, where separation of solid particulate matter from a gaseous stream is undertaken.
Floor sweeping systems employing filters are disclosed in detail in U.S. Pat. No. 3,233,274, dated Feb. 8, 1966, Merville O. Kroll, entitled "Sweeping Machine Dust Separator Apparatus", and U.S. Pat. No. 3,639,940, dated Feb. 8, 1972, Alfred D. Carlson and Joseph G. Kasper, entitled "Filter Chamber", both patents being assigned to Tennant Company, the same assignee as the present invention. In U.S. Pat. No. 3,639,940, a vibratory shaking mechanism for filter bags is disclosed. The present invention relates to a modified form of shaking mechanism for removal of dust from filter bags so as to achieve even more effective removal of the dust particles collected on the surface of the filter bags.